Finely dice the onion. In a large skillet, cook the onion in the vegetable oil until translucent (2-3 minutes on medium low). Add the curry powder, turmeric, cardamom, bay leaves, chili powder, and salt. Stir and cook until the spices are fragrant (2-3 minutes).
Peel then cube the sweetpotato into ¾ inch cubes while the onion and spices cook. Once fragrant, add the sweetpotatoes to the skillet, turning up the heat to medium. Stir well to coat sweetpotatoes in the onion and spice mixture, then put a lid on the skillet and let cook for 20 minutes until the sweetpotatoes are just fork tender but maintain their shape.
While the filling is cooking, roll out the pie dough and cut out 5-inch circles.
Once the sweetpotato filling is cooked, flip off the heat and let the filling cool to the touch. Remove bay leave. Preheat the oven to 375°
Fill each 5-inch dough round with 2-3 Tbsp of room temperature sweetpotato filling and crimp the edges. Place on a lightly greased baking pan. If desired, brush the pastry with an egg wash to yield a darker golden color. Bake the curry puffs for 17-20 minutes until a dark golden color. Serve warm or at room temperature.